Turbochargers are commonly used to increase the power of a vehicle engine. Turbochargers include a turbine which generates pressurized air, and the air is forced into the engine to increase combustion pressure, and therefore increase the power generated by the engine.
With some tubocharging systems, a portion of the pressurized air is bled off to create a vacuum and induce flow of purge vapor. The vacuum created is used as part of a purge system, where the purge system directs purge vapors from a fuel tank through various conduits to redirect the vapors into the intake manifold of the engine, and burn off these vapors through combustion.
Current turbo purge systems use a venturi vacuum generator (such as a vacuum pump) to allow purge of the evaporative system while the turbocharger is activated (i.e., the intake manifold is under positive pressure). This vacuum pump often uses significant amounts of the pressurized air created by the turbocharger, thereby reducing the power increase created by the turbocharger. However, it is desirable to use as much of the pressurized air as possible to maximize the power increase to the engine. In order to limit the amount of turbo air running through the pump, and temporarily maximize engine power, a turbo bypass switching valve (BSV) has been used to alter the amount of flow going to the vacuum pump (venturi nozzle).
However, this approach still reduces the efficiency of the turbocharger by diverting some of the pressurized air to the vacuum pump, instead of the intake manifold of the engine. It is therefore desirable to maximize the efficiency of the vacuum pump, and minimize the amount of airflow diverted from the turbocharger.